Radio wire connectiho circuits



July 20, 1926.

R. BOWN ET AL RAPID WIRE CONNECTING CIRCUITS 4 Sheets-Shoat 1 original Filed April 26, 1921 INVEN TORS A TTORNE Y July 20 192 6. 7

R. BOWN El AL mwro mm comlscum cmcuu;

011mm Filed p i 1921 4 Shoots-Shoot 2 N TORS L M45012 BY I E RN A TTORNEY Jul" 20 g 1926.

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RADIO III! COIIIBCI'IIG CIRCUITS gum Filed April 26. 1921 4 Mil-Slit. 3

'IN VENTORS @ZTLWLSM/ rfpmvsy July 20 I926. V R. BOWN ET AL mm mm comwc'rllm cmcun-s 4 Shoots-Sheet 4 Original Filed pril 26, 1921 i 25 one of a number of correspon ting and receiving chamiels of the-radio Reissued July 20, 1926.

I Mien STATES PATENT ome;

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invention relates to connecting circyits and more particularly to connecting or link circuit for establishing connections between wire lines and radio systems. 0 systems, as now developed, and particularly radio telephone systems, invo'live atrans mit-ting station and a receiving station,-usually located some distance apart,

as for example, a mile or so. 'In order to rtlime reaction of the radio transmitter upon the radio receiver, the transmitti station-may be provided with acfilnraiity channels for transmitting to es of several distant receiving stations and flthe receiving station may likewise .be provided with a corresponding number of receiving channels for simultaneously receiving messages from saiddistant stations. "In ,0 at the communication facilities provi d by such a radio system may be extended o er I i I cei'vn g'station of the radio-amt.

.wire telephone or telegraph circuits, itis desirable that some arrangement be provided for interconnecting any long distance telephone circuits, for exam5le, wit-h any ingtransnntsystem. I

There are certain factors which make the tinctly difl'erent in some important from similar operation of wire or ri'ier circuits. The radio receiving station and the radio transmitting station, although located a short distance apart, must he brought'to a common point with the toll line terminal that they may be properly connected vv:for a through circ1i' from wire to radio. It is further desire 10 that this condition be duplicated at both the transfieidently on any :and -a ll radio channels. -must lbe able to monitoc aunt has up between-redid an m was-- operation of a radio telephone system dis-i mitting and receiving station oftlie radio I to listen or to talk and listen: simultaneously orwinicteurthermore, the operator should "be able f before making tbefi'nal through connections on a call, to adjust the gai-ns'on either the transmitting or receiving side the dircuit sothat a properoomrmmiealtion will resul. Arrangements are, of course, also necessary for signaling over toll wire circ'liit or for s1 stations. It shou be possible ior any cell to be monsltmed from the nonaperating station; that is to-say, it tjon is hein' carried from the reoeiying station bear it shoilildg at the same time, be posa'ble to monitor alleonnectionfifinfl (the transmitting station board as wet}; Finally, we vision'mnet be made jor-the-oper'ator to cut over quickly and neadily to an order wire connecting the trflting and re- In Hm in e'ntion,

connecting or-link circitits axe yfiwided and so as tointecoonneet wire 'with radio channels, in such a mimnner as to satisfy the foregoing as It is obviously meemr'y toll line which is bmughtup to \the radio necessary switching and arrangements may he introduced- These are in the two wir e line or in the four-(wine part of the circuit. In accordance widrr thepmesent invention, arrangements are provided for performing the switchin operations in accordance mithLea'ther of v methods.

The invention may now he fully understoodfrom vthe zfoilowing description,

'wheninead in connection with the accompanyin drawing, Figs. 1 and 2, of which,

illustr switching circuits at the radio transmitter and radio receiver respectively of a radio system, for inter-connecting the symem with wire lines, the switching ar rangemcut being associated with the 'fiourwine part oi the circuit; and Figs 3 and 4 illustrate azsimilar arrangement in which :the switching we provided in the two-wire part of the ciuuiit.

aling the distant radio Referring to Figs. 1 and 2, Fig. 1 illustrates the apparatus associated with the radio transmitter located at station A, and Fig. 2 illustrates the apparatus at a corresponding receiving station B located a short distance away, the two stations cooperating to simultaneously transmit to and receive from distant radio stations. L designates a toll line terminating at the station A, at which point it is branched through the usual hybrid coil into a circuit LE leading to the radio transmitter and a circuit LW leading from the radio receiver, the circuits LE and LW terminating in jacks JE and JW respectively. The line L is balanced in a well known manner by means of networks N Associated with jack JE is a drop SE or other form of signal responsive device, to indicate the transmission of ringing current over the toll line L,. The cord circuit comprising conductors (WV and CE is provided at station A for controlling the establishment of connections between the circuits LVV and LE and the radio transmitter T and receiver R. For this purpose the conductors CW terminate. in the plugs PW and PW while conductors CE terminate in plu PE and PE,. When it is desired to esta lish connectionsto the radio transmitter and receiver directly at station A, the plugs PW and PE may be inserted into acks JW, and JE, which are connected to circuits LW and LE, respectively, the latter being connected by means of conductors LE to the local transmitter T and the former extending over a circuit leading to the receiver R at the receiving station B.

The radio transmitter T is merely conventionally indicated and comprises a transmittin antenna TA having associated therewith c annels I, II and III for multiplex transmission. Only the apparatus. associated with the channel I is indicated and this apparatus comprises a modulator M of any well known character as, for example, a vacuum tube m0dulatorsaid modulator being supplied with'carrier current of radio frequency from a source 10. The telephone or other signaling currents are applied to the modulator of the channel I over the circuit LE When the establishment of connections between the wire line and the radio system is to be controlled from the receiving station B, the cord circuit illustrated in Fig. 1 may be connected to jacks JW, and JE which are connected to trunks TW and TE leading from station A to station B. In this instance the cord functions merely as a patching cord to extend the circuits LW and LE to station B. The drop SW may be associated with the jack JW to indicate to the operator at station A that a distant radio station desires to be connected to the wire line.

The cord circuit is provided with three switching keys, K K and K all controlling the monitoring, listening and talkin pierations, and with ringing keys K and the former being arranged to transmit ringing current to the wire line and the lat- 900 cycles, and the ringing apparatus of the radio station is so arranged, as will be later described, that it will respond when both of these frequencies are applied alternately, but will not respond to either frequency alone.

The keys K K and K each have three positions in which they may be locked in any well known manner. The springs of the key K, are so arranged that with the key lever in its normal position, the springs on either side of the key lever will be closed. When the insulated element of the key lever is shifted to the left, the springs on the lefthand side will remain closed, but those on the right-hand side will be open, so that the listening and monitoring apparatus will be disconnected from the radio side of the system and will be connected to the wire side of the system exclusively. When the key lever is shifted in the opposite position, the righthand springs will remain closed and the lefthand springs will be permitted to open, so that the operators apparatus will be connected to the radio side of the system exclusively. The keysK and K 3 are similar in construction to ke K except that in the neutral position of the key lever all of the s rings are open and when the insulating e ement is shifted to the right, for example, all of the springs to the right will be closed, and when shifted to the left only the springto the left will be closed. The key K functions to connect the operators talking and listening set either to a plug PO which may be connected to an order wire O through a jack J or to the cord circuit through key K When the key K is adjusted to connect the operators set with the cord set, the key K will determine whether the operators receiver will be connected to the circuit alone for monitoring purposes or whether both transmitter and receiver will be connected to the circuit for talking and listening.

At the station B the trunks TW and TE terminate in jack JTV and J E and a drop SE may be associated with the jack JE to respond to a ringing signal from the line L A cord circuit having conductors CW andCE, is arranged to extend the connection from the circuits TW and TE to the cirmay be used toenable the operator at statmion B to monitor a connection established at station A, by inserting the plugs PWV,, and

- responding to ringi Ahdd V V p v I Fu erdetails of the apparatus may now.

PE, in the jacks JW and M3,. The drop SW, may be associated with pack JW,, for g sitfials incoming from the radio system and operators set at station B ma be connected toithe order wire 0, throng: plug PO,and jack JO, when the key K, 1s operated to shift the insulating element to the right.

The radio receiving a aratus comprises an antenna RA, with w ich may be assoa'atod a pluralit 0d receiving channels I, II, and III. he ohalgmell s i'mhide spiltable filte apparatus 2 an e receiving a pparatus associated with the channel I alone is illustrated. This aparatus includes a demodulator or detector 5,, which may be for example, of the balanced Vacuum tube type, said demodulator connected to the circuits LW and L leading to the switchboards at stations A and B respectively. If desired,

an amplifier A W, may be provided in the output circuit of the demodulator 1),. The ripging responsive apparatus associated with the radio receiver comprises two tuned circuits 11 and 12, connected to the output side ofthe demodulator, these tuned circuits being selective of the detected ringing Y uencies of, for example, 700 and 900 c respectively. Vacuum tube detectors 13 and 14 are associated with the-two tuned circuits and these detectors control the individual windings of a polarrelay PR. "When the-two frequencies of, for example, 706

cycles'and 900 cycles, are alternately recei'ved at some low frequency rate ofin terruption as, for example, 16 intern1p-' tions per second, the winding of re]? RR will be alternately energized to shi 'the arnmture to the right and left at a corresponding low frequency rate, thereby shift battery connections of a local circuit 15 that a low frequency alternating mug ing circuit of 16 cycles per second will be transmitted to the circuits operate the drops SIVS, and SW, .at stations ve y.

beunderstpod from descriptionxof the .operation which is as follows: 7

Assumingthat the control of the establishmei'lt on connection between the wire W and LW, to"

system and the radio system, is to be from station B, the .cord circuit of Fig. 1 will be used as a etching circuit by inserting the plugs P and E, into acks JW, and JE,, and by inserting the "plu PW, and PE, in jacks JW, and JE,. he keys K, and K will be in their normal positions and the sin controlling devices GW, and GE, wilfiie as a simple patching cord. If a distant radio station signal is to be connected over line L, a carrier frequency will be received by the antenna BA from the distant station, said carrier frequency being alternately modulated at a rate of 16 cycles per second, for example, in accordance with frequencies of said 700 and 900 cy es. The detector D functions to detect from the carrier frequency the frequencies of 700 to 900 cycles respectively, and these frequencies are selected by the circuits 11 and 12 to cause the armature of the relay PR to vibrate at a rate of 16 cycles per second, thereby impressing a ringing signal upon the conductors LW, and LW, to actuate the drops SW and SW,. As the operator at station B is to handle the call, the operator at station A will ignore the drop and the operator at station B will answer the call by inserting the plugs PW, and PE, in

the jacks JW, and JE,.

The operator will throw the key K, to open the lefthand springs thereof and the key K will be shifted to close the righthand springs. If desired, the operator may also shift the key K, to open its lefthand springs. The operators transmitter and receiver will now be connected to the radio side of the system, the transmitter being connected to the circuit LE, and the receiver b connected to the circuit LW,. The operator will therefore receive the detected voice message transmitted from the distant radio station, communicating with the calling station by means of her transmitter which is connected to the circuit LE,. The operator is enabled to speak to the distant calling station by transmitting the voice current over 'the circuit LE, and over the circuit LE to the modulator M, so that the carrier frequency circuit L The operator, having determined that the call is for the line L,, may first adjust the gain due to the amplifier AW, by means of the gain adjusting device GW,, this gain adjusting devlce bcmg connected between the amplifier AW, and the operators receiver. The operator may also adjust the gain of the amplifier AE, in the circuit leading-to the radio transmitter, by adjustingthe gain controlling device JE at the sametime throwlng the switch 20 to its open so that the cord functions A ill) lower position in order to shift the connection of the operators receiver from the key K to the transmitting circuit LE It will be seen that the operators receiver is now connected to the output side of the amplifier AE and the gain controlling device will adjust the input current, the operator being enabled to determine when the adjustment is right by listening on the output side of the amplifier. The operator will then re store the switch 20 and shift the key K, to open the righthand springs, thereby disconnecting her set from the radio side of the system and connecting it to the wire side. The plugs .PVV, and PE will then be inserted in the jacks JV and JE and the ringing key K will be actuated to transmit ringing current over the circuit TVV through the cord conductor CWV and over the. circuit LW to the toll line L Having signaled the distance toll operator, the radio operator is enabled to communicate with the toll operator to pass information as to the desired connection. In conversing with the toll operator the radio operator s transmitter will be connected to the circuit TE. and the receiver to the circuit TW so that the transmission over these circuits will take place in directions opposite to the normal direction of transmission when the complete connection between the radio system and the wire system is set up.

The distant toll operator, having obtained the desired subscriber, the key K, will be restored to its neutral position and the conductors of the cord circuit will be extended through from the wire part of the system to the radio part of the system. The called subscriber can now communicate with the calling radio station over a circuit as follows:

From the line L over the circuit LE conductors (3E trunk TE conductors CE, conductors LE including the repeater AE conductors LE to the modulator M and thence by radiation of the antenna TA to the distant station.

Transmission in the opposite direction from the calling radio station to the called subscriber takes place as follows:

The received radio oscillations are impressed upon the receiving antenna RA, passed through the filter F detected by detector D amplified by amplifier AW and then transmitted over the circuit LW conductors CW trunk TlV conductors CW and circuit LW to the line L During the conversation the operator may listen in on the transmission from radio to wire without disturbing the connection, by throwing the key K, to close the lefthand springs thereof, the key K being, of course, in position to connect the operators set with te various cords. Under these circumstances, the talking currents incoming from the circuit LYV to the conductors (ll/V Will pass into the circuit 21 over the lefthand contacts of the key K over the circuit 22 and inner lefthand contacts of the key K to the receiver. The operator may also listen in on the conversation transmitted both ways by throwing the key K to its talking and listening position, so that the righthand springs of the key are closed. Under these circumstances the circuit 21 is connected to the circuit 22 over the inner righthand contacts of the key K and the connection is extended from the conductors CE over circuit 23, outer righthand contacts of key K over the circuit 24, outer lefthand contact of the key K to the operators transmitter. The voice currents passing from the trunk TE to the radio transmitter will flow into the circuit 23 and will be heard by the operator through the transfromer 25 which affords a side tone connection between the operators trans mitter and receiver.

The operation when a subscriber desires to be connected over the toll line to a distant radio station will be somewhat similar. In this case ringing current will be transmitted from the toll line L, over the circuit LE conductors CE, and trunk TE.,,.

thereby actuating the drops SE and SE The operator at station E in response to the actuation of the drop SE will plug into jacks JW and JE and shift the key K, to connect her set to the wire side of the cord, the key K being in talking and listening position. Having ascertained the connection desired, the operator will insert the plugs PW and PE, into the jacks JW, and JE and then shift the key K, to the opposite position and actuate the ringing key'K This will result in alternately applying to the circuit LE currents of 700 cycles and 900 cycles, respectively. These currents will be transmitted through the amplifier AE, and over the circuit LE to the modulator M The carrier frequency from the source 10 will be modulated accordingly and radiated to the distant station where it may actuate the ringing apparatus similar to that illustrated in connection with the radio receiver at station B.

When the distant operator answers the call, the radio operator at station B may communicate with such operator at the same time adjusting the receiving gain by means of the transmission adjusting device GVV As soon as the distant radio operator is ready to receive the call, the key K, can be restored to normal position, thereby connecting the radio circuit through to the wire circuit. Thegain of the amplifier AE in the transmitting circuit may be adjusted as previously described, by shifting the switch 20 to connect the receiver to the circuit LE,,

and by adjusting the transmission device GE; The monitoring operation during'the will he as previously described; During oat these connections, the operator at station A will be-enabled to a monitor in exactly same way as at stationdd, by suitable manipidation of the cord oircuit keys and the operators at the two stations may communicate with each other at any time by shifting their keys K and i K; to'elose their righthand springs, thereby 'connectin the operators sets to the plugs PO, and 0, respectively. These logs w1ll in the jacks-JO, and J 2 respec- Jtively, associated withepposite ends of order .wire 0,, so that conversationmay now i'proceed over the order wire. I

' In the operation previously described it' been assumed that the operator at the station B will'be in charge of the in: in. nt of connections. It is equally poeeiblefhewever, to establish the connectienemt Station A. In this case the trunks I l TW,;'TE,,"theoord circuits CW, and CE at station E and the circuits LW and 11E,

' need notzbe The operator at station Aestahlisheethe connection by inserting the PW, and PE, in thejacks JW, and 516;. ringing signal from a distant "station will operate. the drops SW md SW, as previously described; Where ilheioperator at station A is to establish the connection from radio'to wire in response to a call :Erom a distant radio station, the operalbr at station A will insert the plugs in the as described andbywproper maui tion of the keys K K and K the operatorwill be able to communicate with the distant radio operator; The-message carton transmitted by the operator 'at-dition A =wil ass over the circuits LE h an lnnp or AE nnd over the circuitlL to cha red-i transmitter. In transmitting from the distant station to the o h receiver, the detected voice outrents-"in theioatipat circuit ofdetecmr D, at -B wiil be amplified by amplifier AW, and transmitted over the circuit 13W, and'over'the conductors 0W, of the cord circuit to theoperators receiver. The 0 ratim of' riugirxslggbgfl operator wil "be "eimihrwthat in connection with that ofsetting up a call at etfitio'n B and "need not be further described. As the cord circuit it Mon A is identical with that at stat'um B, the monitming,"talking and listening us of operator will be oldie is those already discussed. The adjustment or the gain of! the repeater AW can be by settin the transmision controlling element G 1 of the upper 'paii' flf of the cord circuit'and :gaim oi the 'nwlifier RE, may be adjmlied by means the e1ement'GE',, the operator-is receiver being switched by means 0 switch into connection withthe lrections, however, the keys K of circuit The manner in which a call incoming from the toll line L, is switched to the radio apparatus, will be obvious without further description, the connection fleeing established by inserting the Ylefthand plugs of the cord circuit at station A into the jacks connected with the toll line, and by lnserting the plu s Pl-V and PE, into the jacks JW, and E,'.

The method o f'operation just described prevents the operator at station E from 'tdking any part in the establishment of a connection. The operator at station B may. however, monitor on a receiving circuit,

that is, on transmission from the radio re ceiver to the toll line, by inserting plugs PW, and'PE, into the jacks JW, and JE,.

The 'keys'K K, and K being thrown to the proper ositions for monitoring, this will connect t e operators receiver to the circuit LW, thereby permitting the operator to listen in on the received transmission.

In order to enable the operator at sta- *tion to monitor, talk and listen in the same manner as the operator at station A, when the connection is established through the cord circuit at station A, a slightly dlfferent method of operation may be employed. In order to obtain this result, the cord circuit at'station B maybe used as a patchin cord by inserting the plugs PW,

and P 3 into the trunk jacks, and the plugs PW, and PE, into the jacks W, and 5B,, The key K, should be in neutral position when the cord is to be used for patching purposes. -With the circuit thus'connected the operator at station A in re onse to a radio call actuating the drop S 2 or in response to a toll fcall operating the drop 8B,, will complete the connect-ion by inserting the plugs PW and PE, in the jacks JW, andJE, as before, and bv insertingthe plugs PW and PE into the .jacks JW and JE,. Transmission will now take lace, both ways, throi h the cord circuit a? both positions, and eit er operator may monitor or may talk and listen.

When connections are to be established in this manner, the gain controlling device 'GW, and GE, at station '3 should be 0 on so that the adjus'tment of the gain wil be under the conno! of the operator at station A.

It will be noted that the cord circuits are so arranged that an operator may monitor on any number of connections simultaneously. This may be done by throwing the key K, which is common to all of the cords, to such a position as to close its lefthand sgr'mgs, the keys K individual to each of t 'e cords being likewise thrown to close their lefthand springs. When the operator desires to use her set for establishi, eon- 7 other core circuits than the one used in the establishingconnectioii, should be in neutral position in order to prevent the conversation between the operator and the calling parties from being transmitted to establish connections. Monitoring on all connections simultaneously should therefore be taken care of by the operator at station B when the operator at station A is establishing connections, or vice versa.

The arrangement illustrated in Figs. 1 and 2 involves arrangement in which the toll line is split into a four-wire circuit, at the point where it is brought up to the first position of the radio system, and the toll circuit is therefore extended through the two positions at the transmitter and receiver respectively as a four-wire circuit.

.A modified arrangement is illustrated in Figs. 3 and 4, in which the toll circuit is carried through the two stations as a twowire circuit and at the second of the two stations is split into a four-wire connection, one pair leading to the radio transmitter and the other to the radio receiver.

Referring to Figs. 3 and 4, L designates a toll line terminating at the transmitting station A in jack J,. A cord circuit C, is provided at this station, terminating into plugs P and P for use in extending the toll line to station B. A trunk T extends between stations A and B. terminating at the former in a jack J and at the latter in a jack J At station B a similar cord circuit C, terminating in plugs P, and P, is provided for extending the trunk connection to the point at which the two-wire circuit is split into a four-wire circuit. A jack J, is provided at this point and the two-wire circuit terminates in the usual hybrid coil arrangement .whereby the circuit may be split into two branches, one branch LE leading to the radio transmitter and the other branch LlV leading to the radio receiver. The balancing network N is provided for balancing the two-Wire circuit.

Here again the establishment of a connection may be under the control of the operator either at station A or B. If the connection is to be established at station A, the cord-circuit G at station B will be used as a patching cord; if the connection is to be established at station B the cord circuit at station A will be used as a patching cord. Both cord circuits are identical and are provided with controlling keys similar to those of the cord circuits shown in Figs. 1 and 2. The keys K, and K and their connections, are identical to the corresponding keys in Figs. 1 and 2. The keys K and K are also similar in construction to the corresponding keys in Figs. 1 and 2, and perform somewhat the similar functions, but the circuit connections are slightly dlfi'erent. The key K for example, when its lefthandsprings are closed, establishes a monitoring circuit, but the monitoring circuit does not extend to the conductors of the cord but extends over an independent connection 40 to a trunk connection LW' leading from the station A to the output side of the amplifier AW of the'radio receiver at station B. In the talking and listening position of the key K on the other hand, the operators transmitting and receiving circuits are extended as four-wire circuits from the righthand contacts of the key K and are then merged by means of a hybrid coil arrangement into a two-wire circuit 42 bridged across the talking conductors of the cord 0,. The connections of the key K, at station B are similar, the monitoring connections being established over conductors 43 leading to circuit LVV, on theoutput side of the amplifier AW While in the talking and listening position of the key the trans mitter and receiver of the operator are connccted through a four-Wire circuit," to a hybrid coil merging into a connection 44 bridged across the talking conductors of cord 0,.

The key K, is arranged so that when in neutral position the two ends of the cord will be connected together with the talking and listening connection 42 bridged across the cord. The l our inner contacts of the key are normally closed in the neutral position and the two outer contacts are normally open in this POSltlOIL' When the key is thrown to shift its insulating element to the left, the normally closed springs at the right are open and the talking and listening connection extends toward the toll line exclusively and is disconnected from the radio part of the system. The extreme lefthand contact of the key is also closed to shortcircuit the circuit LE, over the conductors 41'to prevent any singing in the radio system due to the unbalancing of the hybrid coil when the line side ofthe balancing circuit is open. When the key is shifted to the opposite position, the lefthand normally closed contacts are open and the talking and listening connections are to the radio side of the system exclusively. The extreme righthand contact of the key is also closed to complete a circuit through the relay 45 which functions to disconnect the normal balancing network N and substitute an auxiliary network N, so that the hybrid coil to take care of the balance under the changed impedance conditions due to the fact that the impedance of the operators set is difi'erent from that of the toll line. The key K is similar to the key K, its extreme lefthand contact controlling a short circuit over the circuit LE leading to the radio transmitter and its extreme righthand contact controlling the relay 45 to change the net work so as to balance the operators set.

The ringing keys K K K and K are y' kgi ggt at the circuit; for:

' o as simildr: to host uaedi ii'oudinmry cord cir du'rta'emcepb that the'by's K and K are urnmged'to alternately connect two diflermt frequencies to'the rudio'side of: the sys- Mm "described-in. connection with the corres nding liieys-oliligs. 1 and 2.

audio .mmam- T andthe radio receiver R are similar to: the corresponding in I5 I15 and 2, an need' not be described:

'Eli! gain controlling devices are not'associnteel witih mwi record circuits in Figs. B and 4; but are included in the four-write em le, the in controllingulev 'lce tarliand-GE; are bri god across (innit LE lesdlingto the radio tranlmitter at slstions A and B ms tively, and she-gain controlling devices W and are bridgd across a briwcirca'it' lfi leading 1mm the-conductors L associating the" radio receiver with the twowire pdrt ofthe Further details 04 the apparatus may now be understood from the description of the operstion which is as follows:

Lu'hll Of OMEG- tioms to mmaeiesymm is to be controlled at stpfion B, the cord cirenit C ot station! A will be plugged M0 thejnehs J and J -to serve as 'a! psmshin?b cord ion extendin the toll' lineli mu t tank T where it terinmates in the J Iii-response to a ringingsignaht drops SE; and SE, wi ll be acmated m the operator at station E, obsewing'tihe arctmtionoithe- SE will the lug- F; ofthe cord into-the "8614 3- ml 1 t m the hey H so thfltits saluting eremem is moved to the left. 'H is doses the circuit summation- 5o across-theeenflucfiors LE, and! revents the singing of flie system-from the" radio transw the-"radio receiver due to unbalmemes use care circuit is new open.

Hytkrbwhe the K; tU-lose-its right- Hand @fli'igh'alfl% key K; to em its lefthand s rings, theopetuters set is-eom owef-cdhmils 454 304151! to ll circuit, to the-exclusions? the maiupm at the sye eemwna'wile o ra wt is-emored-w'cmem with the callin 'eperatoe' or subscriber: 7

ponm the were! information m .-'I .5 to -He exlendedfeverthe radio channel illus mad-fate inserts the P; in thd'jack-J key 1 inthe dheetios weosnewternew the o'fth systemex'clhsiv'ely. rm

4 o enwrmy then enhance the key K5 to s it ringing'curren k over the eons-neflfihilflvbtsifionzhaffiecerrid o *Wer the vwire circuit and over the More Mywmnplethigtheeennectien the operator adjusts the gains of the amplifiers AE; and. EWV In order to adjust the gain oi the amplifier AW the key K may be thrown to close its 'letthend springs, thereby connecting the operators receiver over circuit 43 to the output side of the amplifier AW The gain controlling device (FW which is bridged across the output circuit of the amplifier, may then; be adjusted so that the desired gain is obtained as determined by the sound in the operators receiver. The operator may then throw the switch 201:0 its lower position thus bridging the receiver across the circuit LE on the 0' Ht side'of the amplifier AE The gain 0' this amplifier may be adjusted by means of the ad usting device G13 During the continuance of the connection the operator may monitor on the circuit leading to-the radio receiver by maintaining the key K in the position in which the lcfihaand spdings are closed. If the key is thrown to the opposite position, the operator will; be enabledtol listen and! talk at any time by reason of the fact that the op.- emtors set is bridged: across the cord circmit llllIOfgh conductors 44. By throwing the hey to claw its lefthwnd springs, the. operatorsset may be connected to the order wine O sothatrthe operators at stavtions A and may communicate with each other. 3

A call firom radio to wire is handled in a somewhat similar manner;- A ringing signal from an distant radio station operates the apparatus in a manner similar to tlrat described in connection with Fig. 2, and transmits a; ringing'cdrrent to conductors'LW; and LW thereby actuating the drops SW, and S\V The operator M station' B then pl into the jack J and throws the key to shiit its insulating element to the-right. This connects the 'opemtors set to the radio side of the system exclusively 8nd closes the extreme right? hand contest to complete a circuit through the relay 45, which substitutes the balancing arran ement M for the balancing arrangement 4 the former balancing arrangement being designed to balance the impedance of the operators set. Having ascertained the connection desired, the plug P will be inserted in thejack J and the rin'ging key K operated. Durin this period the key K may be shifted to itsopposite position tspermit the radio operator to conversewith the'toll operator. When the conversation is ready to proceed, the-key K will be again set in neutral position.

When it is desired to complete connections difference being that the operator observes the actuation of drops SE and SW instead of drops SE, and SWV The key K when its extreme lefthand contact is closed, short circuits the connection LE over conductors 41 to prevent singing between the radio transmitter and receiver when the hybrid coil is unbalanced. When the key is thrown to its opposite position, the extreme'righthand springs control the circuit of the relay 4:) over conductor 51 in a manner similar to that described in connection with key K,. The adjustment of the gain may be controlled by means of the devices Gr! and GE, the former of which is bridged across the output circuit of the amplifier AW through the circuit LW and the latter of which is bridged across the circuit LE on the output side of the amplifier A12 The gain may be observed through the operators receiver by throwing the key K to close its lefthand springs when the ain of amplifier AW, is to be adjusted and by throwing the switch 30 to its lower position when the gain of the amplifier AE is to be adjusted. It will, of course, be understood that when the adjustment is to be made at station A the gain adjustin devices at station B will be disconnected: and when the adjustment is to be made at station B, those at station A will be disconnected.

The circuit arrangements hereinbefore described are quite flexible and adapt themselves to a number of different methods of operations varying somewhat from those described, and as thesedifierent methods of operation will depend somewhat on the conditions under different installations, it will not be attempted here to describe all of the possibilities inherent in the apparatus as these features will be readily apparent to one skilled in the art.

It will also be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated, without departing from the spirit of the invention as defined in the following claims.

What is claimed is:

1. In'a signaling system a radio transmitter and radio receiver, connections extending from said radio transmitter and said radio receiver to a common point, a hybrid coil and a balancing means for associating said connections with a two-wire terminal, a plurality of wire communication channels and a link circuit independent of said hybrid coil for associating said radio transmitter and receiver with any one of said wire com munication channels.

2. In a signaling system a station having a radio transmitter thereat, a station having a radio receiver thereat, connections extending to said radio transmitter and said radio receiver, said connections having tertions, trunks for each set of channels ex- '6'- tending between the stations, a plurality of wire communication channels terminating at the other station, means to patch the trunks at one station to the terminals of connnunication channels atthat station, and means at the other station for variably interconnecting the trunks and the communication channels terminating at the other stallOll.

4. In a signaling system a station having a radio transmitter including'a plurality of radio transmitting channels thereat, a station having a radio receiver including a plurality of corresponding radio receiving channel's thereat, connections for corresponding sets of transmitting and receiving channels terminating at one of said stations, trunks for each set of channels extending between the stations, a plurality of wire communication channels terminatin at the other station, switching means at bot stations adapted to variably inter-connect the trunks and communication channels at said stations, said switching means also serving as patching connections so that when variable connections trunks and communication channels are to be controlled from one station, the switching means at the other station may be used to patch the trunks to the communication channels at the other stations.

5. In a signaling system, a radio transmitter and radio receiver having connections leading to a common point, a plurality of wire communication channels connected to said point, link circuits each adapted to interconnect any wire communication channel with the connections leading to said radio transmitter and radioreceiver by having its opposite ends connected to said wire communication channel and said radio connections, respectively, and means associated with each link circuit for enabling the ope-rator to talk and listen on said wire communication channel exclusively or on said radio connections exclusively while maintaining both ends of said link circuit in connection with said wire channel and radio circuit, respectively.

6..In a signaling system, a radio transbetween the i ilitt niafld' radio receitmr'haxingictmnections leadm to a common point, a plflidlityydi. channels connected to said point; link cirizuits reach ada '=to;i'n-

-thrcqnhet'sanywirecommunication channel with the connections leading to said radio transmitter and radio receiver by having its opfldsilid 6538mm tt'xisaid wire communication channel and said radio connections, respectively, means associated with each link circuit for enabling the operator to talk and listen on said wire communica tion channel exclusively or on said radio connections exclusively while maintaining both ends of said link circuit in connection with said wire channel and radio circuit, respectively, and means associated with said lmk circuits for permitting the operator to monitor the connection without interrupting it.

In a si aling system, a radio transmitter and ra i0 receiver having connections leading to a common point, a plurality of wire communication channels connected to said tgfilnt, link circuits each having terminal swi g arrangements at opposite ends thereof, the switching arrangement at one end of the link functioning to connect said link to any one of said wire communication channels, and the switching arrangement at the other end of the link functioning to connect said link to the connections leading to said radio transmitter and radio receiver, and switching means associated with each link circuit to enable the o erators set including the transmitter an receiver to be connected over said'first switching arrangements to the wire channel exclusively, or over the second switching arrangement to the radio part of the circuit exclusively,

'while maintaining both ends of said link circuit connected over said switching arrangements to the wire channel and the radio circuit, respectively.

8. In a signaling system, a radio transmitter and radio receiver having connections leading to a common point, a plurali of wire communication channels connecte' to said celver, switching means associated with each link circuit to enable the operators set including the transmitter and receiver to be connected over said first switching arrangements to the wire channel exclusively, or over the second switchin arrangement to the radio part of the circuit exclusively, while maintaining both ends of said link circuit. mnnected; dzer islfidcswitzhi g2 are. fangdnents to; haawirechaniiebandth nadio circuit, and means asebciat'ldjyith said link circuits to permit the receivercohtlie ,oiien, ato'rs set; to be. associated. with the' connectiim without? 9. In a signaling System 1 azradini trans: mitter-and a; radio re'oeiveryna transmission channel extending from a common point to the radio transmitter and a receiving channel extending from a common point to the radio receiver, amplifying means associated with each channel, a plurality of wire communication channels leading to said common point, link circuits for interconnecting any wire channel with said radio transmitting and receiving channels, and means whereby the operator having control of said link circuits may adjust the gain in either direction at any time.

10. In a signaling system a radio transmitter and a radio receiver, a transmission channel extending from a common pointto the radio transmitter and a receiving channel extending from said common point to the radio receiver, amplifying means associated with each channel, a plurality of wire communication channels leading to said common point, link circuits for inter-com necting any wire channel with said radio transmitting and receiving channel and means whereby the operator having control of said link circuits may adjust the gain in either direction at any time and means whereby the operator may observe the effect of the gain adjustment.

11. In a signaling system, a station having a radio transmitter includin transmitting channel, a station aving a radio receiver including a radio receiving channel, connections for said transmitting and receivin channel, terminatin at one of said stations, a trunk for sai set of channels extending between the stations, a plurality of wire communication channels terminating at the other station, a means to patch the trunk at one station to the terminals of said communication channels at that station, and means at the other station for variably inter-connecting the trunk and the communication channels terminating at said other station.

12. In a signaling system, a station having a radio transmitter includin a radio transmitting channel, a station laying a radio receiver including a radio receiving channel, connections for said set of chan nels terminating at one of said stations, a trunk for said set of channels extending between the stations, a plurality of wire communication channels terminating at the other station, switchin means at both stations ada ted to varia ly inter-connect the trunk an wire communication channels at said stations, said switching means also a radio sel vin as a patchini station so that when variab e connections etween the trunk and wire communication channels new be controlled from one station, the switching means at the other station may be used to patch the trunk to the wire communication channels at the other station In witness whereof, I have signed mv name to this specification this 28th day of May, 1926.

RALPH BOWN. In witness whereof, I have si ed my name to this specification this 2m day of June, 1926.

EDWARD L. NELSON. 

